Design organizations have increased profit margins by focusing on their core competencies of design and development of products and outsourcing manufacturing. Contract manufacturers can be more cost effective because of manufacturing expertise, flexibility, infrastructure, scalability, and global locations. However, to be more cost effective design organizations and contract manufacturers must reliably exchange the information needed to manufacture the products. Computers, the Internet and TCP/IP protocols, the Web, relational databases, mass storage systems, and enterprise software provide infrastructure for information exchange, but problems still persist.
Design organizations transmit several types of design documents to the contract manufacturer. One type of design document is the bill of materials, abbreviated BOM, which lists the parts and materials needed to assemble a product. Another type is the approved manufacturing list (AML), which also lists the approved part and material suppliers.
Maintaining the integrity of the BOM and the AML over the product life cycle is difficult, because the cycle can last several years and costs drive the design organization to change the data in its AML many times. Also, high tech products typically have many parts, thus the BOM may list several thousand parts and the AML 2-3 times more. Some design organizations make this even less manageable by maintaining a single list for all product offerings resulting in AMLs of, e.g., 50,000 to 100,000 parts. Thus, an AML typically lists many part and material suppliers, each which can change offerings, numbering, and prices of parts during the product life cycle.
Contract manufacturers can manually check the data contained in the BOM and AML against data provided by reputable sources to catch errors before parts are ordered. For example, checking the parts against a part supplier's catalog can detect error before the part is ordered. This may be adequate when the number of part numbers in the BOM and AML are small and there is sufficient time to carefully check. Also, workers can detect and correct errors or interpret the intent of the document without the need to change the original document. However, even conscientious workers may commit errors when comparing lengthy lists of parts identified by alphanumeric codes, and it is expensive to check the parts by functional descriptions.
Although manual processing is fault tolerant, many design documents are now transmitted over the Internet and might be input to computers. However, computers do not have the fault tolerance of humans, and small errors can propagate, amplify, and create large problems. Some documents are incomplete when transmitted and only completed when received. The documents may be also transmitted each time the document changes even when most of the document has not changed or transmitted on a periodic basis even when no changes were made. Care must be taken not to overlay the additional information or corrections that may have been made based on the earlier transmissions of the documents.
As a result, many organizations check the prototype to ensure everything is correct in the BOM and AML. Errors found in the prototype are used to correct the data used to purchase the parts and assemble the product. In some cases the original document is corrected but in others only the data used by the contract manufacturer is corrected. However, the contract manufacturer cannot assume that if the prototype works, the BOM or AML is correct. The fact is the prototype only passed certain tests, which may be inadequate to catch all errors, and catching them later may delay product introduction, particularly, if the product is complex, and involves parts with long lead times. Worse, the lack of integrity in the BOM and/or AML may not be discovered until after the product goes into mass production, resulting in recalls. Because of these problems, contract manufacturers must maintain the integrity of the BOM and AML.
FIG. 1A illustrates a contract manufacturer that receives a new version of a design document and simply uses the data to produce the product. This is rarely acceptable, because errors in the documents may result in a defective product that goes into mass production.
FIG. 1B illustrates a contract manufacturer that receives a new version of the design document, uses the data without checking its integrity, but checks the prototype for errors produced as a result of errors in the new version. This will help find errors before mass production, but is labor intensive and error prone.
FIG. 1C illustrates a contract manufacturer that receives a new version of the design document, and manually validates and corrects the data in the design document before using it. A dictionary of correct data is used for validation and correction of the design document. However, manual validation is labor intensive and error prone over the product life cycle, and errors found in one version of a design document may reappear in subsequent versions of the document.
The BOM and the AML are now described in more detail. Each part listed in the BOM and AML should have a unique part number for identification so similar but different parts are distinguishable and to facilitate automated processing by creating systematic naming of the parts independent of part characteristics.
Below is a simplified example of a BOM:
Part NumberQuantityDescription1231electronic product45651-kiloohm resistor78931-microfarad capacitor5671printed circuit board (PCB)6781application specific integrated circuit (ASIC)
As shown above, the BOM of the electronic product 123 lists five 1-kiloohm resistors, three 1-microfarad capacitors, a PCB, and an ASIC. Assembly instructions and drawings describe how the electronic product will be assembled.
The second document is the AML, which lists all of the parts with their approved suppliers:
Below is a simplified example of the AML:
SupplierPart NumberQuantityDescriptionSupplierPart Number1231electronic product45651-kiloohm resistorAcme23478931-microfarad capacitorAcme345″31-microfarad capacitorSmith4675671PCBJones6781ASICAdams
The AML lists the approved resistor is the Acme 234, the approved 1-microfarad capacitors are either the Acme 345 and the Smith 467, Jones supplies the PCB 567, and Adams the ASIC 678. Because the PCB and ASIC are custom manufactured, they do not have a supplier part number. The symbol ″ below part number 789 indicates there are alternative sources of the capacitor. Once the design organization selects its parts from the approved suppliers, the contract manufacturer can assign its own part numbers so the parts can be ordered again.
Now assume the design organization introduces an error in the AML:
Part NumberQuantityDescriptionSupplier Part Number1231electronic product45651-kiloohm resistorAcme 23978931-microfarad capacitorAcme 345″31-microfarad capacitorSmith 4675671PCBJones6781ASICAdams
Assuming that the first AML is correct, the error is that the resistor is misidentified as part number 239. If undetected, the contract manufacturer will order the wrong resistor. A worker may detect the error by noting Acme part number 239 is not a 1-kiloohm resistor, but this is not a reliable way to correct the error.
The added part numbers for the PCB and ASIC must be protected from being overlaid (e.g., overwritten) when the design organization sends a new version of the AML to add, change, or remove parts in the AML. For example, the design organization may remove the Smith capacitor because it costs more than the Acme capacitor producing an AML as follows:
Part NumberQuantityDescriptionSupplier Part Number1231electronic product45651-kiloohm resistorAcme 23978931-microfarad capacitorAcme 3455671PCBJones6781ASICAdams
Because the contract manufacturer did not protect the correction of the misidentified resistor part number in this example, the incorrect resistor part number 239 reenters the AML when the design organization sent the new version of the AML. This illustrates some of the reasons there is a need to shift the work of comparing, updating, filtering the data found in design documents from workers to computers.